With the wireless communication industry thriving tremendously in recent years, handset systems or wireless network systems all adopt wireless transmission systems to transmit information. Transmissions among base stations, or between the base stations and handsets, wireless network cards or the like, have to rely on antennas. A wireless transmitter outputs radio frequency power, which is sent to an antenna through a transmission line, and radiated by the antenna in the form of electro-magnetic waves. At a receiving location, another antenna receives the electro-magnetic waves, which are sent to a wireless receiver through another transmission line. Hence the antenna is an important device in the transmission and reception of electro-magnetic waves. Without the antenna, wireless communication cannot function at all.
Although wireless communication does not have spatial restriction, the electro-magnetic wave tends to attenuate when encounters obstructions (such as walls, metal barriers or the like) in the transmission direction. As a result, receiving quality at the receiving end could be undesirable. In general, if an antenna is designed with a selected transmission direction characteristics, it is called a directional antenna. It aims to enhance the power of the antenna in the selected direction to increase the transmission distance. Such type of antenna usually has a reflective plate on one side, to increase the directionality of the antenna and boost the gain of the antenna, thereby an improved transmission quality may be achieved.
For instance, R.O.C. patent publication No. 558080 discloses a dipole antenna equipped with a reflective plate. It includes a dipole antenna and a reflective plate. Its main feature is that the reflective plate has an opening. The reflective plate is located on one side of the dipole antenna at a selected distance. The shortest distance between the dipole antenna and the reflective plate is ¼λ. The reflective plate can reflect radiated signals for transmission and receiving, to increase the directional radiation gain of the dipole antenna.
Although the reflective signal of the dipole antenna can increase the directional gain, the reflective plate is designed with a bending angle. Moreover, the directionality is omni-directional. For antennas that require a higher directionality, the directional gain is not satisfactory. Moreover, the design of the reflective plate is too complicated and difficult to assemble and install. Hence to enhance the antenna directionality, and simplify the design of the reflective plate to facilitate installation of the antenna system, issues still remain to be resolved.